The aortocoronary bypass for coronary atherosclerosis is a quantum step in surgery for coronary artery disease. The concept of the bypass and the demonstration that it is applicable to a high percentage of patients with arteriographically proven severe symtomatic coronary atherosclerosis is the essence of this advance, not the saphenous vein per se. Several other recent coronary operations were as enthusiastically lauded during the first two to three years following their introduction. Much of the mistaken enthusiasm for the two most recent procedures--the Vineberg implant, the endarterotomy and gusset procedure--was based on the demonstration of angiographic patency alone without regard to quantity of flow or its effect on myocardial function. This project is designed to study the early and late patency in a consecutive series of aortocoronary venous bypass grafts and to measure bypass flow in the early and late followup up period, as well as total coronary flow before and after bypass surgery. These flow data will be correlated with tests of myocardial function. Additionally this study will focus on causes for bypass failure, specifically related to changes in the venous graft such as intimal hyperplasia of the proximal anastomosis. Late occlusion of the venous bypass by intimal hyperplasia appears to be a serious problem limiting the applicability of this procedure.